After the significant breakthrough in 2005, when researchers at UCLA introduced what's unofficially referred to as "tabletop fusion," fusion research, particularly research in pyroelectric fusion, is now on the rise. This breakthrough had enormous implications: by gently heating a pyroelectric crystal in a deuterated atmosphere, one can generate fusion under desktop conditions.  Prior to that, attempts to produce fusion in a room temperature solid-state setting, including "cold" fusion and "bubble" fusion, have met with deep skepticism.  Now, however it has been show that pyroelectric crystals have been shown to be useful materials for the production of low-cost, portable X-ray sources. 
This report aims to discuss the new developments in pyroelectric fusion research and the potential commercial applications of this new research.
Due to the pyroelectric effect, temperature changes cause charge to be developed on the faces of a pyroelectric crystal perpendicular to the axis of polarization. The surface charge density σ, neglecting losses, is given by the change in temperature multiplied by a factor γ, the materially specific pyroelectric coefficient.  Therefore, to find the total charge, one only needs the area of the piezoelectric crystal. Fusion neutrons are produced by heating and cooling two crystals in opposite geometry (i.e., the z+ surface of one crystal facing the z- surface of the other crystal) in ~3 mTorr of D2 gasv. During heating, the crystals become depolarized, resulting in a negative charge on one crystal and a positive charge on the other crystal. A very common example of a piezoelectric crystal is lithium tantalate (LiTaO3); it has been demonstrated that the electric field created by LiTaO3 is sufficient to eject electrons, ionize gas, and create X-rays when the crystals are heated or cooled to vacuum. 
Pyroelectric fusion offers several advantages over other energy sources: most pyroelectric sources have advantages over conventional sources, in that they are low cost, only consume a few watts of power, and are smaller than most sources. They have thus far not reached the neutron yield available from electrostatic confinement sources or portable neutron generators (PNGs). However, they share the advantage of being able to be turned off to eliminate shielding concerns, and can be very compact and inexpensive.  The current generation of pyroelectric neutron sources does not produce neutrons at a high enough intensity to be useful commercially, but that is slowly changing. In 2007, a study in Applied Physics Letters demonstrated a 5.6-fold increase in neutron production. The researchers - exploiting neutron generation via D-D fusion  - were able to increase the yield of neutron production by using paired crystals (which allows one to superimpose the field from two crystals ) and by attaching the copper disk to the crystal with nonconductive epoxy instead of conductive epoxy. 
© Firas Abuziad. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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